Refrigerating unit

Abstract

A refrigerating unit capable of optimum operation with respect to load by finely changing the operating capacity in response to changes in load, and offering energy saving effects. The refrigerating unit has a scroll type inverter-driven compressor and scroll type constant-speed compressors; a pressure sensor installed on the suction side; a circuit for starting the inverter-driven compressor first; and a circuit for deciding the driving frequency of the compressor and the number of constant-speed compressors to operate, based on a suction pressure value detected by the pressure sensor after the compressor was started.

What is claimed is:  
     
       1. A refrigerating unit having an inverter-driven compressor using a variable driving frequency, and constant-speed compressors using a constant driving frequency, said refrigerating unit comprising: 
       a pressure sensor installed on the suction side of the inverter-driven compressor and said constant-speed compressors;  
       means for starting said inverter-driven compressor first, and  
       means for deciding a driving frequency of said inverter-driven compressor or the number of the constant-speed compressors to operate, based on a suction pressure value detected by said pressure sensor after said inverter driven compressor is started, wherein when said suction pressure value rises above a specified value, one or more of said constant-speed compressors is started regardless of the driving frequency of said inverter-driven compressor.  
     
     
       2. A refrigerating unit according to claim  1 , wherein when the suction pressure value falls below a specified value, said constant-speed compressors are stopped regardless of the driving frequency of said inverter-driven compressor. 
     
     
       3. A refrigerating unit according to claim  1 , wherein said constant-speed compressors are started one by one after the driving frequency of said inverter-driven compressor has reached the maximum value. 
     
     
       4. A refrigerating unit according to claim  1 , wherein said constant-speed compressors are stopped one by one after the driving frequency of said inverter-driven compressor has reached the minimum value. 
     
     
       5. A refrigerating unit according to claim  1 , wherein the maximum and minimum values of the driving frequency of said inverter-driven compressor are set, and said constant-speed compressors are started one by one after the maximum frequency has been reached, and said constant-speed compressors are stopped one by one after the minimum frequency has been reached. 
     
     
       6. A refrigerating unit according to claim  1 , wherein said inverter-driven compressor and said constant-speed compressors are of scroll type, wherein when a value detected by said pressure sensor at starting the compressor is greater than a preset value, said inverter-driven compressor and said constant speed compressors are started, and thereafter the driving frequency of said inverter-driven compressor and the number of constant-speed compressors to operate are decided. 
     
     
       7. A refrigerating unit according to claim  1 , wherein said inverter-driven compressor and said constant-speed compressors are of scroll type, 
       wherein the driving frequency of said inverter driven compressor and the number of constant-speed compressors to operate are decided based on a suction pressure value detected by said pressure sensor and the capacity can be controlled in a range of 15% to 100%.  
     
     
       8. A refrigerating unit according to claim  1 , wherein said inverter-driven compressor and said constant-speed compressors are of scroll type, said refrigerating unit further comprising: 
       means for determining a failure of an inverter for driving said inverter-driven compressor, wherein when said inverter is determined to be out of order by said failure-determining means, operating capacity control is continued by changing the number of compressors operating, including said inverter-driven compressor and said constant-speed compressors.  
     
     
       9. A refrigerating unit according to claim  1 , wherein said inverter-driven compressor and said constant-speed compressors are of scroll type, 
       said means for starting starts the operation of said inverter-driven compressor when a suction pressure value (Ps) detected by said pressure sensor is greater than a preset value (PsU);  
       said means for decreasing decreases the driving frequency of said inverter-driven compressor according to a difference between the suction pressure value (Ps) and the preset value (PsU) when the suction pressure value has risen above a specified value (C) after said inverter-driven compressor is started; and said refrigerating unit further comprising means for starting a constant-speed compressor after the driving frequency was decreased.  
     
     
       10. A refrigerating unit, comprising: 
       an inverter driven compressor having a variable driving frequency;  
       at least one or more constant speed compressors;  
       a pressure sensor installed on the common suction side intake of the inverter driven compressor and the at least one constant speed compressor to detect suction pressure; and  
       a controller connected to the inverter driven compressor, the at least one or more constant speed compressors and the pressure sensor, wherein the controller activates the inverter driven compressor first and then the at least one or more constant speed compressors are activated based solely upon the suction pressure being above a predetermined value and said activation of the at least one or more constant speed compressors being completely independent of the driving frequency of the inverter driven compressor.  
     
     
       11. The refrigerating unit recited in claim  10 , wherein the controller deactivates the at least one or more constant speed compressors when the suction value falls below a predetermined value, said the activation is completely independent of the driving frequency of the inverter driven compressor. 
     
     
       12. The refrigerating unit recited in claim  10 , wherein the controller after activating the at least one or more constant speed compressors determines the driving frequency of the inverter driven compressor to optimize operating capacity of the refrigerating unit. 
     
     
       13. The refrigerating unit recited in claim  10 , wherein to the one or more constant speed compressors further comprises: 
       a first constant speed compressor;  
       a second constant speed compressor, wherein the controller activates the first constant speed compressor based upon the suction pressure and then activates the second constant speed compressor based upon only suction pressure, the activation of the first constant speed compressor and the suction constant speed compressor are independent of the driving frequency of the inverter driven compressor.